1. Field of the Invention
The present invention, in general, relates to excavation and, more particularly, to excavating deep basements.
As real estate becomes increasingly valuable, there arises a growing need to maximize usable space. This is especially true in large cities and other urban areas where available building sites are few and lot sizes tend to be smaller in size.
To maximize space, there are only two directions to go on any given construction site and they are either up or down. Construction in an upward direction is well known, as skyscrapers have been in existence for well over a century.
While there is often a desire to build upward as much as possible, there are practical limits as to how high a building can be constructed. City ordinances may limit height. Additionally, there may be soil, foundation, geological and topography considerations as well as other location-specific concerns. Also, as the height of a building progressively increases the cost begins to rise disproportionately with increasing height.
Construction in a downward direction is also well known. Basements predate even the first skyscraper. A basement is a story below the main or ground floor. A basement (sometimes also referred to as a “cellar”) is one or more floors of a building that are either completely or partially below the ground floor. While basements have also been long known there are practical limits how far down they can be built.
Basement space can be utilized in any number of ways. Common uses include additional habitable space that may be used for office, living or even commercial space. Another common use of basement areas is to provide storage space and a location for building utilities. Basements have also long been used to provide a parking area for automobiles.
The maximum practical depth for a basement is limited, in part, by the difficulty and cost of excavation. For some time, the deepest basements tended to be thirty feet deep or less. This depth can be excavated using prior art machines working at grade, such as cranes or other large machines designed for excavation.
However, even deeper basements are now sometimes desired, especially in cities. For example, in cities like San Francisco, Calif., sixty to eighty foot deep excavations (also referred to as “digs” in the industry) are, at times, required.
However, there are numerous serious deficits that arise when prior art excavation techniques are used to excavate this deep (i.e., greater than 30 feet down to approximately an 80 foot depth).
The first is simply a lack of available real estate at or beside the “dig” area (i.e., construction site) that can be used for placement of the necessary excavation equipment. Space on adjoining streets is not generally available as any obstruction would impede the flow of traffic.
As used herein, the phrase, “deep basement” is intended to include any basement that requires excavation deeper than thirty feet below grade level. While basements deeper than thirty feet are the primary focus of this invention, its use may also include the excavation of shallower basements.
When a deep basement is required, prior-art solutions involve the placement of a heavy crane beside the excavation site. Basically, excavation to a depth of approximately thirty feet is made using construction equipment that can dig that deep from grade level. When thirty feet is reached the construction equipment is removed and a crane is brought to the site. However, this is a significant undertaking. Use of a crane requires shoring up (i.e. reinforcing) the site just to support the weight and presence of the crane. This must be done before the crane can be positioned adjacent to the excavation.
As the depth of the excavation proceeds, shotcrete or wood lagging is then used to shore the sidewall of the excavation site. Typically, a plurality of spaced-apart holes are bored to a greater depth than required for the excavation, typically eight to ten feet deeper than the maximum excavation depth. A plurality of vertical steel beams are placed in the holes and are set in poured concrete, which is then allowed to cure. As excavation progresses, shotcrete may be applied to the sides and allowed to cure. Angled tie backs using rod or cable and poured concrete are used to provide additional shoring for the sidewall.
The poured concrete is allowed to cure for approximately one week and then the tie backs are tensioned. Excavation is allowed to proceed for another eight to ten feet of depth. Then, the shoring process must, again, be repeated. This is necessary to prevent caving-in of the ground that is supporting the weight of the crane.
This process renders the crane inoperative for approximately six weeks in total for a sixty foot excavation. Having a large, valuable crane sit idle for six weeks is costly and adds significantly to the cost of excavation.
Also, the crane is simply in the way. During excavation, the soil must be removed from the job site as it is excavated. The use of dump trucks is required to haul the excavated materials away. Therefore, the dump trucks need to access the job site as close as possible. The large crane located on the side of the excavation presents a formidable impediment to access by the dump trucks. It is easy to calculate that an enormous volume of material must be hauled away during deep basement excavation.
Also, the crane presents a hazard to anyone in the vicinity. Therefore, no one works under a crane, anyway. Accordingly, presence of the crane precludes simultaneously accomplishing any other job-related work.
Easy access for dump trucks allows for more rapid filling of the dump trucks in succession as well as their passage to job site for filling and away from the job site after filling. Creating or maintaining good access for dump trucks hastens the process.
Additional complications are caused by the nature of the soil being excavated. For example, the deeper soils encountered during excavation in the San Francisco area are often referred to as “Bay mud”. Bay mud is sticky and, as a result, the buckets used to lift it become coated and as little as one-quarter of the material in the bucket actually falls out. This, effectively, decreases the size of the bucket by seventy-five percent. Consequently, the length of time required for excavation can increase dramatically, which in turn increases the time the crane is used and further drives up excavation costs.
Accordingly, there is a need to significantly decrease both the time and cost of deep basement excavation. Ideally, the use of the crane would also be eliminated. Furthermore, it is desirable that the equipment used in deep basement excavation will not impede access by dump trucks and, ideally, would actually improve their loading. Ideally, lighter weight equipment could be lowered into the excavation and used with improved equipment to accomplish excavation of deep basements in a shorter period of time and at significantly lower cost.
A shoring contractor drills holes, including the holes in which vertical steel beams are placed. An excavation contractor presently is hired to handle the excavation. It is also desirable to eliminate the need for one of the contractors by having the remaining contractor perform both the shoring (hole drilling) and the excavation.
There is also another need to more precisely control the release of material into a dump truck. More precise control would prevent over or under-filling or the release of material when a dump truck is not properly positioned to receive the material.
There is also a need to fill the dump truck faster. At present it takes about fifteen to twenty minutes to fill a twelve cubic yard dump truck at an excavation site. If a truck could be filled in as little as four minutes, then multiple dump trucks could be filled in the time it now takes to fill only one dump truck. This would provide a considerable increase in the speed of material removal and, thereby, would lessen the time required for excavation of a deep basement.
Also, it presently costs almost two dollars per minute to operate a dump truck. When considering that many thousands of loads are required during a deep basement excavation, saving as little as a few minutes with each dump truck filling translates to a significant amount of money being saved.
Another existing problem relates to the difficulty and high cost of moving heavy equipment, such as a crane, to and from the job site.
Accordingly, it is desirable to provide machinery for deep basement excavation that can be dismantled and transported in smaller sections to and from the job site. It is also desirable to utilize smaller machinery that can be expanded as the depth of a dig progresses.
There are other problems associated with the prior art use of cranes. They run on large diesel engines and create considerable noise and pollution from their emissions. There is a desire to utilize electric means, such as electric motor(s) wherever possible during a deep basement excavation to lessen noise and decrease pollution by reducing the “carbon footprint” associated with the excavation process.
Before construction at a job site of the actual building can occur, an electrical service must first be installed. Therefore, it is inevitable that an electric service will be installed. If electric motors were used for the excavation, the only impact would be that installation of the electric service would occur sooner. However, this early installation would provide an unexpected benefit in that virtually all of the available electrical power could be used to operate the excavation electric motors as there would be no other significant user of electricity while the excavation is ongoing.
It is also desirable to eliminate the crane and to replace the crane with other machinery that does not create a significant hazard for those working on or below ground level at the job site. This would permit other job-related construction activities to occur concurrently with deep basement excavation activity. This is something that cannot occur with present (i.e., prior art) deep basement construction techniques that require the use of a crane for dig depths in excess of about thirty feet.
Accordingly, there exists today a need for a deep basement excavation system and truck loader that helps to ameliorate the above-mentioned problems and difficulties as well as ameliorate those additional problems and difficulties as may be recited in the “OBJECTS AND SUMMARY OF THE INVENTION” or discussed elsewhere in the specification or which may otherwise exist or occur and that are not specifically mentioned herein.
As various embodiments of the instant invention help provide a more elegant solution to the various problems and difficulties as mentioned herein, or which may otherwise exist or occur and are not specifically mentioned herein, and by a showing that a similar benefit is not available by mere reliance upon the teachings of relevant prior art, the instant invention attests to its novelty. Therefore, by helping to provide a more elegant solution to various needs, some of which may be long-standing in nature, the instant invention further attests that the elements thereof, in combination as claimed, cannot be obvious in light of the teachings of the prior art to a person of ordinary skill and creativity.
Clearly, such a system and method of excavation would be useful and desirable.
2. Description of Prior Art
Cranes and construction equipment are, in general, known. While the structural arrangements of the currently known devices may, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices and methods.